Heat-resistant resin paste and method for producing same

ABSTRACT

An object of the present invention is to provide a heat-resistant resin paste that enables the formation of a precise pattern, exhibits excellent adhesiveness, heat resistance and flexibility, and enables a shortening of the production time, as well as a method for producing thereof. The present invention relates to a heat-resistant resin paste, comprising a first organic solvent (A1), a second organic solvent (A2) that comprises a lactone, a heat-resistant resin (B) that is soluble in a mixed organic solvent of (A1) and (A2), and a heat-resistant resin filler (C) that is soluble in (A1) but insoluble in (A2), wherein (C) is dispersed within a solution comprising (A1), (A2) and (B).

TECHNICAL FIELD

The present invention relates to a heat-resistant resin paste thatexhibits excellent adhesiveness, heat resistance, flexibility andworkability, as well as a method for producing thereof.

BACKGROUND ART

Heat-resistant resins such as polyimide resins exhibit superior heatresistance and mechanical properties, and are consequently already inwidespread use in the electronics field as surface protection films andinterlayer insulating films for semiconductor elements. In recent years,screen printing methods and dispensing methods that do not requirecomplex steps such as exposure, developing, and etching and the like areattracting considerable attention as image formation methods forpolyimide-based resin films used as surface protection films, interlayerinsulating films and stress relaxation materials.

Screen printing methods and dispensing methods typically use aheat-resistant resin paste with thixotropic properties that contains abase resin, a filler, and a solvent as components. Almost all of theheat-resistant resin pastes that have been developed to date have used asilica filler or an insoluble polyimide filler as a thixotropy-impartingfiller, and as a result, large numbers of residual voids or air bubblesare left at the filler interface upon heating and drying, causingproblems that include a deterioration in the film strength and inferiorelectrical insulation properties.

In order to overcome these problems, heat-resistant resin pastes thatare capable of forming polyimide patterns with excellent properties havebeen developed by employing a special combination of an organic filler(soluble filler), a base resin, and a solvent in which the filler firstdissolves upon heating and drying, and subsequently forms a co-solublephase with the base resin to form a film (see Japanese PatentPublication No. 2,697,215 and Japanese Patent Publication No.3,087,290).

DISCLOSURE OF INVENTION

However, although the heat-resistant resin pastes described aboveinclude no residual voids or air bubbles at the filler interface uponheating and drying, and therefore exhibit excellent film density andelectrical insulation properties, the production process of theheat-resistant resin pastes requires synthesis of an organic filler (thesoluble filler), and subsequent addition of a solution containing thisorganic filler (soluble filler) dissolved therein to a poor solvent,thereby precipitating the organic filler (soluble filler), meaning thepreparation of the organic filler (soluble filler) requires considerabletime, and requires further improvements in workability.

Accordingly, an object of the present invention is to provide aheat-resistant resin paste that enables the formation of a precisepattern, exhibits excellent adhesiveness, heat resistance andflexibility, and enables a shortening of the production time, as well asa method for producing thereof.

The present invention provides a heat-resistant resin paste thatexhibits excellent adhesiveness, heat resistance and flexibility, inwhich thixotropic properties are imparted to the heat-resistant resinpaste, and which is capable of forming a precise pattern by screenprinting or dispensing methods, by using a heat-resistant resin fillerthat is soluble in a first solvent but insoluble in a second solvent.More specifically, the present invention relates to a heat-resistantresin paste in which, by selecting an organic solvent comprising alactone as the second organic solvent, the preparation of theheat-resistant resin filler and the production of the heat-resistantresin paste can be conducted within the same solvent in a comparativelyshort period of time, thus enabling an improvement in the productivityfor producing the heat-resistant resin paste.

In other words, the present invention relates to a heat-resistant resinpaste comprising a first organic solvent (A1), a second organic solvent(A2) that comprises a lactone, a heat-resistant resin (B) that issoluble in a mixed organic solvent of (A1) and (A2), and aheat-resistant resin filler (C) that is soluble in (A1) but insoluble in(A2), wherein (C) is dispersed within a solution comprising (A1), (A2)and (B).

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the first organic solvent (A2)comprises a nitrogen-containing compound.

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the nitrogen-containing compound isa heterocyclic nitrogen-containing compound.

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the lactone is eitherγ-butyrolactone or γ-valerolactone.

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the heat-resistant resin (B) andthe heat-resistant resin filler (C) are polyimide resins or precursorsthereto.

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the heat-resistant resin (B) and/orthe heat-resistant resin filler (C) is a polyimide resin or precursorthereto obtained by reaction between: a diamine comprising an aromaticdiamine represented by a general formula (I) shown below:

(wherein, R₁, R₂, R₃ and R₄ each represent, independently, a hydrogenatom, an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 1 to 9carbon atoms, or a halogen atom, and X represents a single bond, —O—,—S—, —SO₂—, —C(═O)—, —S(═O)—, or a group represented by a formula shownbelow)

(wherein, R₅ and R₆ each represent, independently, a hydrogen atom,alkyl group, trifluoromethyl group, trichloromethyl group, halogen atom,or phenyl group), and/or a diamine comprising an aromatic diaminerepresented by a general formula (II) shown below:

(wherein, Y represents —O—, —C(═O)—, —S(═O)—, or a group represented bya formula shown below);

and a tetracarboxylic acid comprising an aromatic tetracarboxylicdianhydride represented by a general formula (III) shown below or aderivative thereof:

(wherein, Z represents a single bond, —O—, —S—, —SO₂—, —C(═O)—, or—S(═O)—).

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the thixotropic index of theheat-resistant resin paste is 1.5 or higher.

Furthermore, the present invention also relates to the heat-resistantresin paste described above, wherein the heat-resistant resin filler (C)is a filler that is prepared within the second organic solvent (A2).

Furthermore, the present invention also relates to a method forproducing the heat-resistant resin paste described above, wherein theheat-resistant resin filler (C) is prepared within a second organicsolvent (A2) that comprises a lactone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing an example of a diode that usesa heat-resistant resin paste of the present invention as an insulatingfilm. In the figure, 1 represents an electrode, 2 represents theinsulating film, 3 represents an oxide film, and 4 represents a chip.

FIG. 2 is a cross-sectional view showing an example of a semiconductorpackage that uses a heat-resistant resin paste of the present inventionas a stress relaxation layer. In the figure, 11 represents the stressrelaxation layer, 12 represents a solder ball, 13 represents anelectrode, 14 represents a silicon wafer, 15 represents apolyimide-based insulating film, and 16 represents an aluminum pad.

BEST MODE FOR CARRYING OUT THE INVENTION

As follows is a more detailed description of a heat-resistant resinpaste of the present invention.

A heat-resistant resin paste of the present invention comprises a firstorganic solvent (A1), a second organic solvent (A2) that comprises alactone, a heat-resistant resin (B) that is soluble in a mixed organicsolvent of (A1) and (A2), and a heat-resistant resin filler (C) that issoluble in (A1) but insoluble in (A2).

(A1) First Organic Solvent

There are no particular restrictions on the first organic solvent (A1)used in the present invention, provided that when the solvent is used asa mixed solvent with the second organic solvent (A2), the mixed solventdissolves the heat-resistant resin (B) but does not dissolve theheat-resistant resin filler (C), and provided that the first organicsolvent (A1) alone dissolves the heat-resistant resin filler (C). Thefirst organic solvent (A1) alone preferably also dissolves theheat-resistant resin (B). Specific examples of (A1) include ether-basedcompounds such as diethylene glycol dimethyl ether, diethylene glycoldiethyl ether, triethylene glycol dimethyl ether and triethylene glycoldiethyl ether, sulfur-containing compounds such as dimethylsulfoxide,diethylsulfoxide, dimethylsulfone and sulfolane, ester-based compoundssuch as cellosolve acetate, ketone-based compounds such ascyclohexanone, and methyl ethyl ketone, nitrogen-containing compoundssuch as N-methylpyrrolidone, N,N′-dimethylacetamide,N,N′-dimethylformamide,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone,1,3-dimethyl-2-imidazolidinone and various amines, and aromatichydrocarbon-based compounds such as toluene and xylene, and thesecompounds may be used either alone, or in combinations of two or moredifferent compounds.

The first organic solvent (A1) used in the present invention preferablycomprises a nitrogen-containing compound. There are no particularrestrictions on the nitrogen-containing compound, and suitable examplesinclude the aforementioned N-methylpyrrolidone, N,N′-dimethylacetamide,N,N′-dimethylformamide,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone,1,3-dimethyl-2-imidazolidinone and various amines, although heterocyclicnitrogen-containing compounds are preferred as they offer particularlysuperior dissolution properties.

The heterocyclic nitrogen-containing compound, namely the heterocyclicpolar solvent, preferably dissolves both the heat-resistant resin (B)and the heat-resistant resin filler (C), and specific examples ofheterocyclic solvents that can be used include N-methylpyrrolidone,1,3-dimethyl-3,4,5,6-tetrahydro-2(H1)-pyrimidinone and1,3-dimethyl-2-imidazolidinone. When selecting the solvent, selection ofa solvent for which the values for the solubility parameter and thepolarity parameter are similar to those of the dissolution targetmaterial is preferred.

The quantity used of the heterocyclic nitrogen-containing compoundpreferably represents at least 40% by weight, even more preferably atleast 50% by weight, and most preferably 60% by weight or more of thecombined weight of the first organic solvent (A1) and thelactone-containing second organic solvent (A2) described below. If thequantity of the heterocyclic nitrogen-containing compound is less than40% by weight, then the solubility of the heat-resistant resin (B) andthe heat-resistant resin filler (C) (both of which are described below)deteriorates, which tends to cause a deterioration in thecharacteristics of the produced coating film.

(A2) Second Organic Solvent that Comprises a Lactone

The second organic solvent (A2) used in the present invention is anorganic solvent that comprises a lactone, and is either a lactone or amixed solvent of a lactone and another solvent. There are no particularrestrictions on the second organic solvent (A2) provided that when thesolvent is used as a mixed solvent with the first organic solvent (A1),the mixed solvent dissolves the heat-resistant resin (B) but does notdissolve the heat-resistant resin filler (C), and provided that thesecond organic solvent (A2) alone does not dissolve the heat-resistantresin filler (C). In the present invention, the quantity used of thelactone, relative to the total weight of the second organic solvent(A2), is preferably at least 5% by weight, and is even more preferablywithin a range from 5 to 95% by weight, even more preferably from 10 to90% by weight, even more preferably from 15 to 90% by weight, and mostpreferably from 15 to 85% by weight. Provided the quantity used of thelactone is at least 5% by weight, the thixotropic properties of theobtained paste fall within a range that ensures favorable handlingcharacteristics for the paste, and provided the quantity is no greater95% by weight, the solubility of the heat-resistant resin (B) and theheat-resistant resin filler (C) are less likely to deteriorate, meaningdeterioration in the characteristics of the produced coating film can bemore readily prevented.

Examples of suitable lactones include γ-butyrolactone, γ-valerolactone,γ-caprolactone, γ-heptalactone, α-acetyl-γ-butyrolactone, andε-caprolactone, and these lactones may be used either alone, or incombinations of two or more different compounds. Of these lactones, ifdue consideration is given to the usable time period during applicationof the heat-resistant resin paste, then high boiling point lactones suchas γ-butyrolactone and γ-valerolactone are preferred.

In those cases where a mixed solvent of a lactone and another solvent isused as the second organic solvent (A2), there are no particularrestrictions on the other solvent mixed with the lactone, provided thesolvent is co-soluble with the lactone, and examples of suitablesolvents include ether-based compounds such as diethylene glycoldimethyl ether, diethylene glycol diethyl ether, triethylene glycoldimethyl ether and triethylene glycol diethyl ether, sulfur-containingcompounds such as dimethylsulfoxide, diethylsulfoxide, dimethylsulfoneand sulfolane, ester-based compounds such as cellosolve acetate,ketone-based compounds such as cyclohexanone, and methyl ethyl ketone,nitrogen-containing compounds such as N-methylpyrrolidone,dimethylacetamide and1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, and aromatichydrocarbon-based compounds such as toluene and xylene, and thesesolvents may be used either alone, or in combinations of two or moredifferent solvents.

In consideration of the usable time period during application of theheat-resistant resin paste, the boiling points of the organic solvents(A1) and (A2) used in the present invention are preferably 100° C. orhigher. Furthermore, the boiling point of the mixed solvent of (A1) and(A2) is preferably within a range from 100 to 250° C.

(B) Heat-Resistant Resin

There are no particular restrictions on the soluble heat-resistant resin(B) of the present invention, provided the resin is soluble in the mixedsolvent of (A1) and (A2), and is preferably soluble at any temperaturewithin a range from −25° C. to 150° C. Specific examples of suitableresins include polyimide resins, polyamideimide resins and polyamideresins, although of these, polyimide resins and precursors thereto arepreferred in terms of the heat resistance, etc. The heat-resistant resin(B) is preferably soluble in the first organic solvent (A1) alone, andis even more preferably soluble at any temperature within a range from−25° C. to 150° C. The heat-resistant resin (B) may be insoluble in thesecond organic solvent (A2) alone.

As follows is a more detailed description of polyimide resins and theprecursors thereto. Examples of methods for obtaining the abovepolyimide resins or precursors thereto include methods in which adiamine comprising an aromatic, aliphatic or alicyclic diamine compoundis reacted with a tetracarboxylic acid comprising a tetracarboxylicdianhydride or derivative thereof, and this reaction can be conducted inthe presence of an organic solvent. The reaction temperature ispreferably within a range from 25° C. to 250° C., and the reaction timecan be selected appropriately in accordance with factors such as thescale of the batch and the reaction conditions employed.

There are no particular restrictions on the diamine comprising anaromatic, aliphatic or alicyclic diamine compound, or thetetracarboxylic acid comprising a tetracarboxylic dianhydride orderivative thereof that are used in preparing an aforementionedpolyimide resin or precursor thereto, although if due consideration isgiven to solubility within the mixed solvent of the first organicsolvent (A1) and the second organic solvent (A2) that comprises alactone, then the use of a compound represented by a general formula (I)and/or a general formula (II) shown below as the diamine is preferred.

(wherein, R₁, R₂, R₃ and R₄ each represent, independently, a hydrogenatom, an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 1 to 9carbon atoms, or a halogen atom, and X represents a single bond, —O—,—S—, —SO₂—, —C(═O)—, —S(═O)—, or a group represented by a formula shownbelow)

(wherein, R₅ and R₆ each represent, independently, a hydrogen atom,alkyl group, trifluoromethyl group, trichloromethyl group, halogen atom,or phenyl group).

The general formula (II) is shown below.

(wherein, Y represents —O—, —C(═O)—, —S(═O)—, or a group represented bya formula shown below)

Specific examples of compounds of the above general formula (I) include2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[3-methyl-4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]butane,2,2-bis[3-methyl-4-(4-aminophenoxy)phenyl]butane,2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]butane,2,2-bis[3,5-dibromo-4-(4-aminophenoxy)phenyl]butane,1,1,1,3,3,3-hexafluoro-2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,1,1,3,3,3-hexafluoro-2,2-bis[3-methyl-4-(4-aminophenoxy)phenyl]propane,1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane,1,1-bis[4-(4-aminophenoxy)phenyl]cyclopentane,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]ether,4,4′carbonylbis(p-phenyleneoxy)dianiline and4,4′-bis(4-aminophenoxy)biphenyl, and of these,2,2-bis[4-(4-aminophenoxy)phenyl]propane is the most preferred.

Specific examples of compounds of the above general formula (II) include4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone,3,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenyl ether,3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,3,4′-diaminobiphenyl, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenoneand 1,4-bis(4′-aminophenyl)benzene, and of these, 4,4′-diaminodiphenylether is the most preferred.

In the present invention, the aromatic diamine compound represented bythe general formula (I) and/or the general formula (II) preferablyrepresents from 1 to 100 mol %, and even more preferably from 2 to 100mol %, and most preferably from 5 to 100 mol %, of the total weight ofthe diamine compound.

In the present invention, aromatic diamines other than those representedby the above general formula (I) may also be used, and suitable examplesof such diamines include m-phenylenediamine, p-phenylenediamine,diamino-m-xylylene, diamino-p-xylylene, 1,4-naphthalenediamine,2,6-naphthalenediamine and 2,7-naphthalenediamine.

Moreover, examples of other diamine compounds that can be used besidesthe aforementioned aromatic diamine compounds as the diamines includealiphatic diamines and diaminosiloxanes, etc., such as1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane,1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane,1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane,1,11-diaminoundecane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane and1,3-bis(3-aminopropyl)tetramethylpolysiloxane.

These diamines may be used either alone, or in combinations of two ormore different compounds.

The tetracarboxylic dianhydride or derivative thereof is preferably anaromatic tetracarboxylic dianhydride represented by a general formula(III) shown below or a derivative thereof:

(wherein, Z represents a single bond, —O—, —S—, —SO₂—, —C(═O)—, or—S(═O)—).

Specific examples of compounds represented by the above general formula(II) include tetracarboxylic dianhydrides such as3,3′,4,4′-biphenyltetracarboxylic dianhydride,2,2′,3,3′-biphenyltetracarboxylic dianhydride,2,3,3′,4′-biphenyltetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride,3,4,3′,4′-benzophenonetetracarboxylic dianhydride,2,3,2′,3′-benzophenonetetracarboxylic dianhydride and2,3,3′,4′-benzophenonetetracarboxylic dianhydride, as well asderivatives of these dianhydrides, and of these, the use of3,3′,4,4′-benzophenonetetracarboxylic dianhydride is preferred.

These dicarboxylic acids may be used either alone, or in combinations oftwo or more different compounds.

There are no particular restrictions on the organic solvent used in thepreparation of the polyimide resin or precursor thereto that functionsas the heat-resistant resin (B), and suitable solvents includeether-based compounds such as diethylene glycol dimethyl ether,diethylene glycol diethyl ether, triethylene glycol dimethyl ether andtriethylene glycol diethyl ether, sulfur-containing compounds such asdimethylsulfoxide, diethylsulfoxide, dimethylsulfone and sulfolane,ester-based compounds such as γ-butyrolactone and cellosolve acetate,ketone-based compounds such as cyclohexanone and methyl ethyl ketone,nitrogen-containing compounds such as N-methylpyrrolidone,N,N′-dimethylacetamide, N,N′-dimethylformamide,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone,1,3-dimethyl-2-imidazolidinone and various amines, and aromatichydrocarbon-based compounds such as toluene and xylene, and althoughthese solvents may be used either alone, or in combinations of two ormore different solvents, in order to enable subsequent conversion to aheat-resistant resin paste, the use of the first organic solvent (A1) ispreferred.

In the present invention, the heat-resistant resin (B) preferably has anumber average molecular weight, determined by gel permeationchromatography (GPC), that falls within a range from 1,000 to 200,000,even more preferably from 2,000 to 180,000, and most preferably from3,000 to 160,000.

(C) Heat-Resistant Resin Filler

The heat-resistant resin filler (C) is insoluble in the mixed solvent of(A1) and (A2), and is preferably insoluble at least one point within arange from −25° C. to 250° C. Furthermore, the heat-resistant resinfiller (C) is soluble in the first organic solvent (A1) alone, and ispreferably soluble at least one point within a range from −25° C. to250° C. Moreover, the heat-resistant resin filler (C) is insoluble inthe second organic solvent (A2) alone, and is preferably insoluble atleast one point within a range from −25° C. to 250° C. Provided thefiller meets these requirements, there are no other particularrestrictions on the heat-resistant resin filler (C), and specificexamples of suitable fillers include resin fillers comprising polyimideresins, polyamideimide resins, polyamide resins, or precursors thereto,which can be selected appropriately in accordance with the solventsused. Of the various possibilities, polyimide resins or precursorsthereto are preferred in terms of their heat resistance.

Next is a detailed description of the resin filler comprising apolyimide resin or precursor thereto. Examples of methods of obtainingthe polyimide resin or precursor thereto that functions as theheat-resistant resin filler include methods in which a diaminecomprising an aromatic, aliphatic or alicyclic diamine compound isreacted with a dicarboxylic acid comprising a tetracarboxylicdianhydride or derivative thereof, and this reaction can be conducted inthe presence of an organic solvent. The reaction temperature ispreferably within a range from 10° C. to 120° C., and even morepreferably from 15° C. to 100° C. If the reaction temperature is lessthan 10° C., then the reaction tends not to proceed satisfactorily,whereas if the temperature exceeds 120° C., then precipitation of thefiller tends to be inadequate. The reaction time can be selectedappropriately in accordance with factors such as the scale of the batchand the reaction conditions employed.

There are no particular restrictions on the diamine and dicarboxylicacid used, and the same compounds as those used for the heat-resistantresin (B) can be used.

There are no particular restrictions on the organic solvent used duringpreparation of the polyimide resin or precursor thereto that functionsas the heat-resistant resin filler (C), and the same solvents as thoseused for the heat-resistant resin (B) can be used, although in order toenable subsequent conversion to a heat-resistant resin paste, the use ofthe second organic solvent (A2) is preferred.

In the present invention, the heat-resistant resin filler (C) preferablyhas a number average molecular weight, determined by gel permeationchromatography (GPC), that falls within a range from 1,000 to 200,000,even more preferably from 2,000 to 180,000, and most preferably from3,000 to 160,000.

The mixing ratio between the heat-resistant resin (B) and theheat-resistant resin filler (C), reported as a weight ratio, ispreferably within a range from 10/90 to 90 to 10, even more preferablyfrom 15/85 to 85/15, and is most preferably from 20/80 to 80/20.

(Characteristics of Resin Paste)

The thixotropic index of a heat-resistant resin paste of the presentinvention is 1.5 or higher, and preferably 1.6 or higher, even morepreferably 1.7 or higher, and is most preferably 1.8 or higher. Thethixotropic index of the heat-resistant resin paste is measured at ameasurement temperature of 25° C., using an E-type viscometer (RE-80U,manufactured by Tokyo Keiki Co., Ltd.) and a sample size of 0.2 g. Thethixotropic index is represented by the ratio η₁/η₁₀ between theapparent viscosity values η₁ and η₁₀ measured at rotation rates of 1 rpmand 10 rpm respectively. Ensuring that the thixotropic index is 1.5 orhigher enables favorable printing or coating characteristics to be morereadily obtained.

The viscosity of the heat-resistant resin paste (measured at 0.5 rpm:η_(0.5)) preferably falls within a range from 1 to 1,000 Pa·s, even morepreferably from 3 to 900 Pa·s, and most preferably from 3 to 800 Pa·s.If the viscosity of the heat-resistant resin paste is less than 1 Pa·s,then the paste tends to be prone to sagging following printing orcoating, whereas if the viscosity exceeds 1,000 Pa·s, then theworkability of the paste tends to deteriorate.

The concentration of the heat-resistant resin (B) and heat-resistantresin filler (C) within the heat-resistant resin paste is preferablywithin a range from 5 to 90% by weight, even more preferably from 10 to90% by weight, and most preferably from 10 to 80% by weight. If thisconcentration is less than 5% by weight, then achieving a thicker filmfor the product coating tends to become more difficult, whereas if theconcentration exceeds 90% by weight, there is a danger of a loss in thefluidity of the paste, which tends to cause a deterioration in theworkability.

The heat-resistant resin paste of the present invention may alsoinclude, if required, antifoaming agents, pigments, dyes, plasticizers,antioxidants, coupling agents, and resin modifiers and the like.

(Production Method)

According to one embodiment of the present invention, there is provideda method for producing a heat-resistant resin paste that offersexcellent workability, wherein the heat-resistant resin filler (C) canbe prepared within the second organic solvent (A2) that comprises alactone.

A heat-resistant resin paste of the present invention is preferablyobtained by mixing together an organic solvent solution of aheat-resistant resin (B) that is soluble in a first organic solvent(A1), and an organic solvent dispersion of a heat-resistant resin filler(C) that is insoluble in a second organic solvent (A2). The mixing ispreferably conducted at a temperature within a range from 10 to 180° C.,and even more preferably from 15 to 160° C. If the mixing temperature isless than 10° C., then the heat-resistant resin solution and theheat-resistant resin filler dispersion tend not to mix satisfactorily,whereas if the temperature exceeds 180° C., the heat-resistant resinfiller tends to dissolve in the organic solvent, and either result tendsto result in a deterioration in the printing or coating characteristics.

The polyimide resin or precursor thereto that functions as theheat-resistant resin filler (C) is preferably synthesized by a reactionconducted within the second organic solvent (A2) that comprises alactone. The quantity used of the lactone, relative to the total weightof the organic solvent used in the reaction, is preferably within arange from 5 to 95% by weight, even more preferably from 10 to 90% byweight, even more preferably from 15 to 90% by weight, and mostpreferably from 15 to 85% by weight. If the quantity used of the lactoneis less than 5% by weight, then precipitation of the heat-resistantorganic filler tends to take considerable time, causing a deteriorationin the workability, whereas if the quantity exceeds 95% by weight, thensynthesis of the heat-resistant resin filler tends to become moredifficult. Furthermore, the polyimide resin or precursor thereto thatfunctions as the heat-resistant resin (B) is preferably synthesized by areaction conducted within the first organic solvent (A1).

There are no particular restrictions on the method used for convertingthe polyimide resin precursor to a polyimide resin via acyclodehydration, and typical methods can be used. Examples of suitablemethods that can be used include thermal cyclization methods in whichthe cyclodehydration is effected by heating either at normal pressure orunder reduced pressure, and chemical cyclization methods in which adehydrating agent such as acetic anhydride or the like is used, eitherin the presence or absence of a catalyst. In the case of a thermalcyclization method, the reaction is preferably conducted while the watergenerated by the dehydration reaction is removed from the system. Duringthis process, the reaction solution is preferably heated to atemperature within a range from 80 to 400° C., and preferably from 100to 250° C. In such cases, the water may be removed by azeotropicdistillation, by using a solvent such as benzene, toluene or xylene orthe like that forms an azeotrope with water.

In the case of a chemical cyclization method, the reaction is conductedin the presence of a chemical dehydrating agent, at a temperature withina range from 0 to 120° C., and preferably from 10 to 80° C. Examples ofpreferred chemical dehydrating agents include acid anhydrides such asacetic anhydride, propionic anhydride, butyric anhydride or benzoicanhydride, or a carbodiimide compound such as dicyclohexylcarbodiimide.During this reaction, a substance that promotes the cyclizationreaction, such as pyridine, isoquinoline, trimethylamine, triethylamine,aminopyridine or imidazole, is preferably also added. The chemicaldehydrating agent is typically used in a quantity within a range from 90to 600 mol % relative to the total weight of the diamine compound,whereas the substance that promotes the cyclization reaction is used ina quantity within a range from 40 to 300 mol % relative to the totalweight of the diamine compound. Dehydration catalysts, includingphosphorus compounds such as triphenyl phosphite, tricyclohexylphosphite, triphenyl phosphate, phosphoric acid or phosphorus pentoxide,and boron compounds such as boric acid or boric anhydride may also beused. In terms of reducing the quantity of residual ionic impurities,the aforementioned thermal cyclization method is preferred.

A heat-resistant resin paste of the present invention exhibits excellentadhesiveness, heat resistance and workability. By using a lactone as thesecond organic solvent, the productivity associated with producing theheat-resistant resin paste can be improved dramatically. Moreover, aheat-resistant resin paste of the present invention can be used forforming a precise pattern using screen printing or dispensing methods,and a semiconductor device produced using a heat-resistant resin pasteof the present invention exhibits favorable properties.

EXAMPLES

As follows is a detailed description of the present invention based on aseries of examples, although the present invention is in no way limitedto these examples.

Synthesis Example 1 Synthesis of a Solution of a Heat-Resistant Resin(B)

A 1 liter four-necked flask fitted with a thermometer, a stirrer, anitrogen gas inlet, and a condenser fitted with an oil-water separatorwas flushed with a nitrogen stream, while the flask was charged with96.7 g (0.3 mols) of 3,4,3′,4′-benzophenonetetracarboxylic dianhydride(hereafter abbreviated as BTDA), 55.4 g (0.285 mols) of4,4′-diaminodiphenyl ether (hereafter abbreviated as DDE), 3.73 g (0.015mols) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereafter referredto as LP-7100), and 363 g of1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (hereafterabbreviated as DMPU), and following stirring for approximately 6 hoursat a temperature of 70 to 90° C., the reaction mixture was cooled tohalt the reaction, yielding a heat-resistant resin solution (PI-1) witha number average molecular weight (measured using a GPC method, andcalculated against a calibration curve produced using standardpolystyrenes) of 25,000.

Example 1 Synthesis of a Solution of a Heat-Resistant Resin Filler (C)

An identical flask to that used in the synthesis example 1 was chargedwith 96.7 g (0.3 mols) of BTDA, 61.5 g (0.15 mols) of2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereafter abbreviated asBAPP), 27.0 g (0.135 mols) of DDE, 3.73 g (0.015 mols) of LP-7100,133.25 g of DMPU, and 308.59 g of γ-butyrolactone hereafter abbreviatedas γ-BL), and when the mixture was stirred for 5 hours at 70 to 90° C.,a polyimide precursor filler with a number average molecular weight of24,000 precipitated out from the solution. Subsequently, the reactionmixture was cooled to halt the reaction, yielding a heat-resistant resinfiller solution (PIF-1). The thus obtained heat-resistant resin fillerwas soluble in DMPU.

Example 2 Synthesis of a Solution of a Heat-Resistant Resin Filler (C)

An identical flask to that used in the synthesis example 1 was chargedwith 80.5 g (0.25 mols) of BTDA, 97.38 g (0.2375 mols) of BAPP, 3.11 g(0.0125 mols) of LP-7100, 295.62 g of γ-BL, and 126.69 g of DMPU, andwhen the mixture was reacted in exactly the same manner as the example1, a polyimide precursor filler with a number average molecular weightof 25,000 precipitated out from the solution after approximately 7hours, and consequently, the reaction mixture was cooled to halt thereaction, yielding a heat-resistant resin filler solution (PIF-2). Thethus obtained heat-resistant resin filler was soluble in DMPU.

Example 3 Synthesis of a Solution of a Heat-Resistant Resin Filler (C)

An identical flask to that used in the synthesis example 1 was chargedwith 96.7 g (0.3 mols) of BTDA, 61.5 g (0.15 mols) of BAPP, 27.0 g(0.135 mols) of DDE, 3.73 g (0.015 mols) of LP-7100, 419.75 g of DMPU,and 22.09 g of γ-BL, and the mixture was then reacted for 8 hours at 70to 90° C., cooled to halt the reaction, and then allowed to stand for 12hours, yielding a heat-resistant resin filler solution (PIF-3)comprising a polyimide precursor filler with a number average molecularweight of 26,000. The thus obtained heat-resistant resin filler wassoluble in DMPU.

Example 4 Synthesis of a Solution of a Heat-Resistant Resin Filler (C)

An identical flask to that used in the synthesis example 1 was chargedwith 96.7 g (0.3 mols) of BTDA, 61.5 g (0.15 mols) of BAPP, 27.0 g(0.135 mols) of DDE, 3.73 g (0.015 mols) of LP-7100, 44.19 g of DMPU,and 397.66 g of γ-BL, and when the mixture was stirred for 3 hours at 70to 90° C., a polyimide precursor filler with a number average molecularweight of 15,000 precipitated out from the solution. Subsequently, thereaction mixture was cooled to halt the reaction, yielding aheat-resistant resin filler solution (PIF-4). The thus obtainedheat-resistant resin filler was soluble in DMPU.

Comparative Example 1

With the exception of replacing the reaction solvent from the example 1comprising 133.25 g of DMPU and 308.59 g of γ-BL with 441.84 g of DMPU,reaction was conducted in exactly the same manner as the example 1, buteven when the reaction solution was subsequently left to stand for 30days, no polyimide precursor filler precipitated out.

Comparative Example 2

An identical flask to that used in the synthesis example 1 was chargedwith 102.9 g (0.35 mols) of 3,3′4,4′-biphenyltetracarboxylic dianhydride(hereafter abbreviated as BPDA), 70.0 g (0.35 mols) of DDE, and 403.4 gof DMPU, and the mixture was then reacted for 8 hours at 70 to 90° C.,subsequently cooled to halt the reaction, and then allowed to stand for5 days, yielding a heat-resistant resin filler solution comprising apolyimide precursor filler with a number average molecular weight of30,000.

The synthesis conditions employed, and the results for, the examples 1to 4 and the comparative examples 1 and 2 are summarized in Table 1.

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4example 1 example 2 Synthesis Monomer Acid BTDA 1.00 1.00 1.00 1.00 1.001.00 conditions composition component (mols) Amine BAPP 0.50 0.95 0.500.50 0.50 — component DDE 0.45 — 0.45 0.45 0.45 1.00 LP-7100 0.05 0.050.05 0.05 0.05 — Solvent DMPU 30 30 95 10 100 100 composition γ-BL 70 705 90 — — (weight) NV quantity following synthesis 30 30 30 30 30 30(weight %) Results Time required for filler precipitation 5 7 20 3 No128 (hours) precipitate Number average molecular weight 24,000 25,00026,000 15,000 No 30,000 of precipitated filler precipitate

It is evident that by adopting a heat-resistant resin paste andproduction method therefor according to the present invention, aheat-resistant resin filler can be produced in a short time period,thereby providing excellent workability.

Example 5

A 1 liter four-necked flask fitted with a thermometer, a stirrer, anitrogen gas inlet, and a condenser fitted with an oil-water separatorwas flushed with a nitrogen stream, while the flask was charged with 300g of the heat-resistant resin solution (PI-1) obtained in the synthesisexample, and 400 g of the heat-resistant resin filler solution (PIF-1)obtained in the example 1, and the resulting mixture was stirred for 2hours at 50 to 70° C., thereby yielding a heat-resistant resin paste(PIP-1) with the heat-resistant resin dissolved therein and with theheat-resistant resin filler dispersed therein.

The viscosity and thixotropic index of the heat-resistant resin paste(PIP-1) obtained in the example 5 were measured at a measurementtemperature of 25° C., using an E-type viscometer (RE-80U, manufacturedby Tokyo Keiki Co., Ltd.) and a sample size of 0.2 g. The viscosity wasmeasured at 0.5 rpm, whereas the thixotropic index was evaluated bydetermining the ratio η₁/η₁₀ between the apparent viscosity values η₁and η₁₀ measured at rotation rates of 1 rpm and 10 rpm respectively.

In addition, the heat-resistant resin paste (PIP-1) obtained in theexample 5 was also screen printed onto a silicon wafer, using a screenprinting device (LS-34GX fitted with an alignment device, manufacturedby Newlong Seimitsu Kogyo Co., Ltd.), a meshless metal plate formed fromnickel alloy additive plating (manufactured by Nihon Mesh Kogyo Co.,Ltd., thickness: 50 μm, pattern dimensions: 8 mm×8 mm), and a Permalexmetal squeegee (imported by Tomoe Engineering Co., Ltd.), and theprinting characteristics were evaluated.

Following printing, the printed sample was inspected under an opticalmicroscope for blurring and sagging.

Moreover, the resin composition obtained was coated onto a Teflon (aregistered trademark) substrate, and then heated at 350° C. to dry theorganic solvent, thereby forming a coating film with a film thickness of25 μm. Using a dynamic viscoelasticity spectrometer (manufactured byIwamoto Seisakusho Co., Ltd.), this coating film was measured fortensile modulus of elasticity (25° C., 10 Hz) and glass transitiontemperature (frequency: 10 Hz, rate of temperature increase: 2°C./minute).

Furthermore, the thermal decomposition starting temperature (the 5%weight reduction temperature) was measured using a thermobalance.

The results are shown in Table 2.

Example 6

In the example 5, with the exception of replacing the heat-resistantresin filler solution (PIF-1) obtained in the example 1 with theheat-resistant resin filler solution (PIF-2) obtained in the example 2,exactly the same procedure as the example 5 was used to obtain aheat-resistant resin paste (PIP-2) with the heat-resistant resindissolved therein and with the heat-resistant resin filler dispersedtherein.

Example 7

In the example 5, with the exception of replacing the heat-resistantresin filler solution (PIF-1) obtained in the example 1 with theheat-resistant resin filler solution (PIF-3) obtained in the example 3,exactly the same procedure as the example 5 was used to obtain aheat-resistant resin paste (PIP-3) with the heat-resistant resindissolved therein and with the heat-resistant resin filler dispersedtherein.

Example 8

In the example 5, with the exception of replacing the heat-resistantresin filler solution (PIF-1) obtained in the example 1 with theheat-resistant resin filler solution (PIF-4) obtained in the example 4,exactly the same procedure as the example 5 was used to obtain aheat-resistant resin paste (PIP-4) with the heat-resistant resindissolved therein and with the heat-resistant resin filler dispersedtherein.

Comparative Example 3

In the example 5, with the exception of replacing the heat-resistantresin filler solution (PIF-1) obtained in the example 1 with thesolution obtained in the comparative example 1, the same procedure asthe example 5 was conducted, yielding a heat-resistant resin solution(PIP-5).

TABLE 2 Comparative Item Example 5 Example 6 Example 7 Example 8 example3 Heat-resistant resin paste PIP-1 PIP-2 PIP-3 PIP-4 PIP-5 PasteViscosity (Pa · s) 200 210 210 180 30 characteristics Thixotropic index4.5 4.5 4.5 4.0 1.1 Printing characteristics No No No No Yes (presenceof blurring or sagging) Coating film Tensile modulus of elasticity 33003400 3400 3300 3300 characteristics (MPa) Glass transition temperature260 260 260 240 260 (° C.) Thermal decomposition 490 490 490 480 490starting temperature (° C.)

In addition to the examples described above, a variety of heat-resistantresin pastes can be produced in a short time period by using a firstorganic solvent and a second organic solvent, and selecting a lactone asthe second organic solvent, and in each case, the resultingheat-resistant resin paste exhibits excellent paste characteristics andcoating film characteristics. Furthermore, in those cases where a firstorganic solvent and a second organic solvent are not used, or caseswhere a lactone is not selected as the second organic solvent, obtaininga paste which exhibits excellent results across all areas, includingpaste characteristics, coating film characteristics and workability, isimpossible.

INDUSTRIAL APPLICABILITY

A heat-resistant resin paste of the present invention can be used as aprotective film, insulating film, stress relaxation layer, adhesive, orheat-resistant printing ink or the like for a wide variety of devices,including all manner of semiconductor devices, semiconductor packages,thermal heads, image sensors, multi-chip high-density mounting boards,diodes, capacitors and transistors, as well as for a wide variety ofwiring boards including flexible wiring boards and rigid wiring boards,and is consequently extremely useful industrially. FIG. 1 shows anexample of the use of a paste of the present invention as an insulatingfilm for a diode, and FIG. 2 shows an example of the use of a paste ofthe present invention as a stress relaxation layer for a semiconductordevice.

There are no particular restrictions on the method used for forming aprecise pattern using a heat-resistant resin paste of the presentinvention, and suitable methods include screen printing methods,dispensing methods, potting methods, curtain coating methods, reliefprinting methods, copperplate printing methods, and planographicprinting methods.

1. A heat-resistant resin paste, comprising: a first organic solvent(A1), a second organic solvent (A2) that comprises a lactone, aheat-resistant resin (B) that is soluble in a mixed organic solvent of(A1) and (A2), and a heat-resistant resin filler (C) that is soluble in(A1) but insoluble in (A2), wherein (C) is dispersed within a solutioncomprising (A1), (A2) and (B).
 2. The heat-resistant resin pasteaccording to claim 1, wherein the first organic solvent (A1) comprises anitrogen-containing compound.
 3. The heat-resistant resin pasteaccording to claim 2, wherein the nitrogen-containing compound is aheterocyclic nitrogen-containing compound.
 4. The heat-resistant resinpaste according to claim 1, wherein the lactone is eitherγ-butyrolactone or γ-valerolactone.
 5. The heat-resistant resin pasteaccording to claim 1, wherein the heat-resistant resin (B) and/or theheat-resistant resin filler (C) are polyimide resins or precursorsthereto.
 6. The heat-resistant resin paste according to claim 1, whereinthe heat-resistant resin (B) and/or the heat-resistant resin filler (C)is a polyimide resin or precursor thereto obtained by reaction between:a diamine comprising an aromatic diamine represented by a generalformula (I) shown below:

(wherein, R₁, R₂, R₃ and R₄ each represent, independently, a hydrogenatom, an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 1 to 9carbon atoms, or a halogen atom, and X represents a single bond, —O—,—S—, —SO₂—, —C(═O)—, —S(═O)—, or a group represented by a formula shownbelow)

(wherein, R₅ and R₆ each represent, independently, a hydrogen atom,alkyl group, trifluoromethyl group, trichloromethyl group, halogen atom,or phenyl group), and/or a diamine comprising an aromatic diaminerepresented by a general formula (II) shown below:

(wherein, Y represents —O—, —C(═O)—, —S(═O)—, or a group represented bya formula shown below);

and a tetracarboxylic acid comprising an aromatic tetracarboxylicdianhydride represented by a general formula (III) shown below or aderivative thereof:

(wherein, Z represents a single bond, —O—, —S—, —SO₂—, —C(═O)—, or—S(═O)—).
 7. The heat-resistant resin paste according to claim 1,wherein a thixotropic index of the heat-resistant resin paste is 1.5 orhigher.
 8. The heat-resistant resin paste according to claim 1, whereinthe heat-resistant resin filler (C) is a filler that is prepared withinthe second organic solvent (A2).
 9. A method for producing theheat-resistant resin paste according to claim 1, wherein aheat-resistant resin filler (C) is prepared within a second organicsolvent (A2) that comprises a lactone.